In single rotor helicopters, a lifting force and a propulsive force are provided by a main lifting rotor and yaw control is provided by a second, smaller rotor mounted on a vertical stabilizer at the rear or tail of the fuselage. This second rotor, herein the “tail rotor”, is positioned laterally outwardly from one side of the vertical stabilizer and is mounted at the upper end of the vertical stabilizer for rotation about a horizontal axis. Rotation of the tail rotor causes the rotor to generate a sideways airstream. The vertical stabilizer is in this airstream and blocks a significant portion of the airflow. The blockage effect of a conventional vertical stabilizer is detrimental to the function and efficiency of the helicopter. There is a need to reduce the airstream blockage by the vertical stabilizer. A primary object of the present invention is to fulfill this need, both as a retrofit and as a new construction.
A typical helicopter configuration to which the present invention applies is disclosed by U.S. Design Pat. No. D278,227, granted Apr. 2, 1985, to George W. Johnston, Jr., and assigned to Bell Helicopter Textron, Inc.